#include <stdio.h>
//https://blog.csdn.net/weixin_41234001/article/details/79561870

int count = 0; //统计上法数

/*level代表台阶数 step代表步数 */
void solve(int level, int step, int n)
{

    if (level > n)
        return; //超过40则退出
    if (level == n)
    {   
        //步数为偶数,方法+1，步数为奇数时舍弃这一种走法，并且终止
        if (step % 2 == 0) count++;
        return;
    }
    solve(level + 1, step + 1, n);
    solve(level + 2, step + 1, n);
}
int main()
{
    int n = 0;
    scanf("%d", &n);
    solve(0, 0, n);
    printf("%d", count);
    return 0;
}